A coating film formed from a curable organopolysiloxane paint composition as an antifouling coating film for preventing the deposition of aquatic organisms on underwater structures is useful as a substitute for a conventional antifouling coating film containing a harmful substance such as an organic metal. The curable organopolysiloxane antifouling coating film is laminated over the upper layer of an epoxy resin anticorrosive coating film formed on the surface of a base material such as steel from the viewpoint of anticorrosion properties and is generally used as a curable organopolysiloxane antifouling composite coating film.
The curable organopolysiloxane antifouling composite coating film has been conventionally kept an adhesive force between the coating film layers by interposing one or two organopolysiloxane intermediate coating film layers (Tie Coats) between an organopolysiloxane antifouling coating film layer (Finish Coat) and an epoxy anticorrosive coating film layer (Under Coat) to make the whole antifouling composite coating film have a three- or four-layer coating film structure.
However, such an antifouling composite coating film with a multilayer coating film structure has a problem that a coating work period is prolonged to increase a cost, although long-term antifouling properties are obtained.
Patent Literature 1 by the present applicant proposes, for example, a curable organopolysiloxane antifouling composite coating film obtained by directly laminating, on a surface of an epoxy resin anticorrosive coating film, an organopolysiloxane antifouling coating film excellent in both interlayer adhesiveness with the anticorrosive coating film and antifouling performance.
The antifouling composite coating film is a curable organopolysiloxane antifouling composite coating film comprising: [I] an epoxy resin anticorrosive coating film formed from [i] an anticorrosive paint composition comprising (e1) an epoxy resin and (e2) an amine curing agent for an epoxy resin; and [II] an antifouling coating film formed from [ii] an antifouling paint composition comprising a curable organopolysiloxane composition comprising components (A), (B) and (C) below, directly laminated on a surface of the epoxy resin anticorrosive coating film, wherein the curable organopolysiloxane composition is a three-component curable organopolysiloxane composition comprising: (A) a main agent comprising an organopolysiloxane (a1) having at least two condensation reactive groups in one molecule and silica (a2); (B) a curing agent comprising an organosilane having a functional group that can be condensation-reacted with the condensation reactive groups of the above organopolysiloxane (a1) having at least two condensation reactive groups in one molecule and/or a partial hydrolysate thereof (b1); and a curing accelerator (C) containing at least one tin compound (ac) selected from the group consisting of specific tin compounds.
In other words, the antifouling composite coating film according to Patent Literature 1 is obtained by directly laminating the organopolysiloxane antifouling coating film excellent in antifouling performance on the epoxy resin anticorrosive coating film by improving a special tin catalyst.
However, the antifouling composite coating film described in Patent Literature 1 has had problems that when abase coating film is an epoxy resin, coating under low temperature conditions is difficult, curability under an extreme condition (at a low temperature (0° C.)) is poor, and adhesiveness is deteriorated at a low temperature.
Patent Literature 2 proposes an antifouling and anticorrosive coated steel material comprising: an undercoat layer prepared by coating or covering a steel material with an anticorrosive material which is a urethane paint or a polyethylene resin; an intermediate coat layer prepared by coating a paint containing 3% by weight or more of silicone rubber on the undercoat layer; and a top coat layer prepared by applying a silicone rubber paint onto the intermediate coat layer.
However, a urethane intermediate coating paint containing several percent of a silicone component is needed between urethane and silicone antifouling laminated coating films.
Patent Literature 3 proposes an adhesive composition comprising a hydroxyl group-containing urethane resin, an isocyanate compound and 0.02 to 1.5% of an imidazole compound.
However, Patent Literature 3 is directed at an adhesive agent and does not describe a composite coating film including a silicone antifouling coating film.
Such a room-temperature-curable silicone rubber has been excellent in mold release properties and softness but has been susceptible to improvement in adhesiveness and antifouling properties. In general, antifouling properties tend to deteriorate due to improvement in adhesiveness while adhesiveness tends to deteriorate due to improvement in antifouling properties.